Especially when you're using a bootloader, isn't this interval something like 2 seconds? Doesn't that mean that the user has to push the button a long time before the processor can latch it?

Yes, it would be dependent on the specific bootloader used as to how long the bootloader decides to time out and jump to start the preloaded sketch. I've been using the modified Adafruit bootloader for quite awhile sense one benefit is that there is almost no delay at all for the sketch to start on initial power-up. That bootloader also handles WDT interrupts better. Not sure what the delay is on for the new Uno bootloader. Slow to start bootloaders with long startup delays are so 2009.

when you said that it was trackable on geocaching.com, i thought you were saying that it was when the gps received a signal it send an update to geocaching about where the trackable was located. Is this even possible?

when you said that it was trackable on geocaching.com, i thought you were saying that it was when the gps received a signal it send an update to geocaching about where the trackable was located. Is this even possible?

Yes, that's possible and I thought about it. It would need a gprs module like this: http://www.cooking-hacks.com/index.php/shop/arduino/arduino-gprs-module.html

With that one could set up a special server and the box would send it's id and position to this server every time it get's a fix. Then this server could post a log entry to geocaching.com - That could also happen via some kind of sms-gateway because it's easier to send an sms than to make a data connection.

Very cool project... inspired me to get started on a nixie clock a few days ago. I gotta tell ya', making these things from scratch is a real challenge... After scouring over online schematics I just ordered a ton of MOSFETS, schottkys, inductors, HV caps, 25 MPSA42s, etc. from digikey only to realize that to multiplex tubes I also need HV PNP transistors. I'm also using way too many transistors, right now with my current schematic for only four tubes I'm at all 25 MPSA42s, 4 MPSA92s (anode switching), 14 general purpose switching transistors, and total of 13 IC pins just to switch the tubes (not including the pins of the ATTiny45 controlling the high voltage PSU).

Kudos to you for making a very clean, non-parts-intensive build (albeit with the help of some control ICs ).

Well, from a fellow Geocacher (Yes, this is also my GC handle) I think it's cool! I can see something like this, if the actual cache was located on the grounds of an old Nike missile site. (yet another one of my many odd hobbies).. Yes, the terrorist have put a major dent in the hobby, but it still has its fun times.. How long does the whole thing run for, seeing only a 6V supply (or is that 4.8, Rechargable?) being boosted to 180V for the nixie tubes, must be brutal on batteries!

@gelfling6-I think you'll find there are plenty of geocachers on this forum, in fact GPS is one thing that helped me to get in to arduino... Also, a nixie tube only requires about 2mA at 170V. Assuming that he's only firing one tube at a time, that's just 340mW. Even if his driver is awfully inefficient, the draw is still probably under half a watt. Nixie tubes are actually surprisingly efficient IMO, considering the amount of light they put out.

Very cool project... inspired me to get started on a nixie clock a few days ago. I gotta tell ya', making these things from scratch is a real challenge... After scouring over online schematics I just ordered a ton of MOSFETS, schottkys, inductors, HV caps, 25 MPSA42s, etc. from digikey only to realize that to multiplex tubes I also need HV PNP transistors. I'm also using way too many transistors, right now with my current schematic for only four tubes I'm at all 25 MPSA42s, 4 MPSA92s (anode switching), 14 general purpose switching transistors, and total of 13 IC pins just to switch the tubes (not including the pins of the ATTiny45 controlling the high voltage PSU).

Kudos to you for making a very clean, non-parts-intensive build (albeit with the help of some control ICs ).

I don't do any multiplexing, so I'm just using 3 anode resistors, 4 155id1 (= russian version of the SN74141) and 3 4017 binary counters. I drive them directly, because the tubes are brighter this way and I actually need less power because the firing of the tubes is pretty expensive power-wise.

I need the extra 155id1 for the decimal point on two tubes that is driven separately from the digits. I just need two outputs from that driver so I get along with two inputs. Switching on the digit one from this driver lights a decimal point before the second digit and the two is a decimal point in front of the third digit. I also could've wired the point on the first nixie, but I decided that something like .845 would look weird and 0.85 is precise enough for this application.

I also used a prebuilt power supply to get the 180 Volts (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140426808956) once I realized that you have to be very careful on placing the components on the converter to get an efficiency over 80%.

I can highly recommend this, it's not much more expansive than buying the components (Unless you order the MAX1771 that you need as a sample), it's tiny, works perfectly and can be switched off completely via the arduino.

Some comments on power:

With all three tubes lit the circuit draws 500mA and under 100mA without them. The tubes light for about 10 seconds per distance fix and it needs about 60 seconds to get the fix. So there's an average power consumption of 200mA.

The batteries (NiMH D-cells ) have 6000mAH but because of the voltage drop I'm just counting them in for 3000mAh.

That should be enough for 15hours continuous operation, or at 90 seconds per fix, 600 fixes which is enough to find the target coordinates.

[edit]PS: This is where I got the tubes and driver ICs from: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250749058503, they also come with nice pins that you can solder to a board to make your own socket.

In case the auction is gone when you read this - this is the seller: http://shop.ebay.com/buyer.md/m.html . The tubes are called IN-12b.[/edit]

As there seem to be some geocachers here - I have another idea for an arduino-powered traditional geocache.

I'd love to do this myself, but since I'm in the middle of a big city I can't find the right spot to pull this off anywhere near me where I could maintain it.

Here's the idea:

You make a plastic cache-container that can close with a servo from the inside like my reverse geocache. You'll add an arduino, some kind of display mounted in the lid and an rfid reader with the antenna on the bottom of the container. For power supply I'd add a 9V battery holder that can be accessed from the outside.

Then you hide the cachebox in a place from where you can see two distinct landmarks (a bench, some kind of tree stump, etc.). In the cache listing you'll tell the people to bring a 9V battery.

When the cacher finds the cache it won't open. They insert the 9V battery and the display says 'put me on the red mark on the bench behind you'.

There's an rfid card glued under that spot and when the cacher puts the box there the reader sees the rfid and the display says 'Put me on the treestump 200 meters north of here - you have 50 seconds... '. A countdown from 50 begins.

If the cacher does't put the box on the rfid chip in the tree stump within the 50 seconds he has to start over (put it on the bench). If he makes it the box says 'Now back to the bench, you got 45 seconds' and the countdown starts.

If he makes it back to the bench in time the box opens. To close it again he has to take out the battery and put it in again or put the box on a third rfid chip.

Would be real fun if you would install that somewhere where you could watch the people running around

You could also add more rfid stations or make them run faster.

[edit]If you find a spot where there's something like a grid with different field on the ground (like these giant chess boards in parks) you could also make out a kind of puzzle where you have to place the box on different fields with rfids buried in them due to hints on the display. Like just displaying 'A3-D5-F3' with the chess board.[/edit]